C++ References and Java References

Question

//C++ Example

#include 
using namespace std;

int doHello (std::string&);
int main() {
    std::string str1 = \"perry\";
    cout <<         


        

Answer 1

The code you have written in java is equivalent to this C++ code:

int main() {
    std::string *s1;
    s1 = new std::string("perry");
    std::cout << s1->c_str() << std::endl;
    doMojo( s1 );
    std::cout << s1->c_str() << std::endl; // not pieterson
}
void doMojo( std::string *str ) {
    str = new std::string("pieterson");
    std::cout << str->c_str() << std::end;
}

perhaps now you see what happens. The C++ references actually wrap around the pointers.. so without the references your code would look like this:

int main() {
    std::string *s1;
    s1 = new std::string("perry");
    std::cout << s1->c_str() << std::endl;
    doMojo( s1 );
    std::cout << s1->c_str() << std::endl; // now pieterson!
}
void doMojo( std::string *&str ) {
    str = new std::string("pieterson");
    std::cout << str->c_str() << std::end;
}

notice the innocuous ampersand:

void doMojo( std::string *&str ) {

That really is the secret. This, and the previous answer that explains about immutability of java strings should make you appretiate the difference between java and c++ references.

Cheers,

jrh.